Surveyor's tape marked "6285 TRADE LO-VAR MARK KEUFFEL & ESSER CO." and "NBS No 9228." With a coefficient of expansion of about .0000015 per degree Centigrade, Keuffel & Esser's LO-VAR tapes were said to be more stable than ordinary steel tapes that had a coefficient of expansion of .000016 per degree Centigrade. Keuffel & Esser also explained that since LO-VAR tapes were intended for precise base line measurements, they generally carry only the end marks and one or two intermediate marks. This example, however, is marked every 5 meters, and at 12.5 and 37.5 meters. It was tested by the National Bureau of Standards, and belonged to the U. S. Coast and Geodetic Survey. New, it cost $75.
Keuffel & Esser introduced the term LO-VAR to commerce, and applied for a copyright, in 1934.
Ref: Keuffel & Essser, Catalogue (New York, 1936), p. 535.
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